The present invention relates generally to pressure garments, and more particularly to lower body pressure garments such as anti-G suits of the type worn by aviators in high performance, high altitude aircraft or spacecraft.
Operators of performance, high altitude aircraft may be exposed to high levels of acceleration (+Gz acceleration) due to flight maneuvers such as rapid banked turns or pulling out of a dive. As a result of such maneuvers the operator""s fluid column shifts causing pooling of blood in the lower extremities. The associated reduction of blood flow to the retina and brain in severe acceleration environments may cause the operator to experience increasingly diminished vision leading finally to loss of consciousness. To protect against such hazardous conditions, aviators in high performance aircraft typically wear pressure garments known as anti-G suits. Anti-G suits typically comprise a pair of cutaway trousers having bladders covering portions of the abdomen, thighs and ankles. The suit is connected to an anti-G valve in the aircraft that senses the onset of +Gz acceleration and opens to pressurize the anti-G suit bladders. The bladders are restrained against the aviators body so that upon inflation the suit compresses the contacted portions of the lower body causing an increase in the local blood pressure, thereby causing increased blood flow to the upper body and decreased blood flow to the lower body. Near the end of and shortly after WWII, the performance and altitude capabilities of aircraft improved such that aircrews could no longer sustain vision and sometimes consciousness throughout certain flight maneuvers. At that time anti-G pressure garments were developed to protect aircrews from the debilitating effects of high +Gz accelerations. An example of such pressure garments is U.S. Pat. No. 2,495,316 to Clarke, et al, which comprises impermeable inflatable bladders over the abdomen and thighs and a woven fabric covering to restrain expansion and apply pressure to body regions covered by the bladder. While the performance of modern military aircraft has been enhanced significantly over the past several decades, anti-G suit technology has remained largely unchanged. Because of this, the standard anti-G suit has limited capabilities for providing +Gz acceleration protection of the magnitude and duration that now occurs during flight maneuvers. In the totally unrelated fields of anti-shock and trauma treatments, pressure garments that apply distributed pressure loads to the lower body have been developed to reduce blood flow to the lower extremities similar to that required for anti-G protection. Examples of such pressure applying garments are U.S. Pat. No. 5,146,932 to McCabe, Canadian Pat. No. 1080072 to Gottfried and Canadian Pat. No. 1021654 to Poole et al. These garments are insufficient for anti-G protection in that they do not provide sufficient pressurization or an adequate means of active control of pressurization. Furthermore, these pressure garments are constructed primarily with impermeable materials that do not offer any means of thermal conditioning. The prior art has sought to increase anti-G protection in a number of ways but most particularly by increasing the body surface area compressed by the anti-G suit bladders. Examples of such efforts are U.S. Pat. No. 4,674,479 to Jennings et al, which, amongst other improvements, arranged a butt strap, integrated to the abdominal bladder of the conventional modern anti-G suit, so that the strap pulled tight to compress the aviator""s buttocks upon inflation, and U.S. Pat. No. 5,537,686 to Krutz et al, describes a garment to provide full pressure coverage over the aviator""s lower body.
Further attempts to maximize +Gz protection in high performance aircraft have included the use of water columns within the anti-G suit. Examples of such efforts are U.S. Pat. No. 5,153,938 to Epperson, and U.S. Pat. No. 6,450,944 to Reinhard, in which different configurations of water columns in suit systems are used to compress the body of the aviator. In such suit systems the hydrostatic pressure of said fluid column changes rapidly with the onset of +Gz acceleration and is directly proportional to and varies linearly with the internal pressure of the fluid column in the body.
Water column pressure garments also suffer from other deficiencies. The presence of water in the cockpit, in particular, is highly undesirable. Suits incorporating water columns tend to be significantly bulkier and heavier than the conventional pneumatic anti-G suit and require a burdensome amount of support in terms of suit fitting and sizing. To combat these deficiencies, the prior art has continuously reduced the amount of water contained in the columns of such a suit. However, this reduction has effectively diminished the physiological benefit realized from the pressurization of the water columns.
Although the prior art has demonstrated significant increase in +Gz protection over the current standard anti-G suit, the suit systems have introduced additional deficiencies including but not limited to reduced mobility, cockpit interference, excessive thermal burden and enhanced logistical burdens such as maintenance and reliability. In particular, pneumatic pressure garments are typically constructed with air, liquid water and water vapor impermeable, solid film laminate materials for the retention of gas under pressure. Whereas such materials are extremely effective as gas barriers, they also act as a barrier to water vapor, thereby inhibiting the natural dissipation of the aviator""s evaporated perspiration and therefore further act as a barrier to metabolic heat loss. Thus the prior art has enhanced +Gz protection through the increase of pressure bladder coverage on the lower body, this has exaggerated the thermal barrier problem.
Complex and burdensome cooling systems have been integrated to anti-G garment systems to combat thermal stress. Flexible air and liquid impermeable, water vapor permeable material of the type disclosed in U.S. Pat. No. 4,194,041 to Gore et al, has been used for pressure garment constructs as disclosed in U.S. Pat. No. 5,003,630 to Bassick et al. Such materials consist of an interior hydrophilic layer, which prevents flow of gases or liquids but permits the transfer of high concentrations of water vapor that diffuse to the exterior hydrophobic layer where the vapor concentration is relatively lower. A bladder constructed from such materials offers benefit over the said conventional bladder constructs, however, the prior art relies solely on the passive diffusion of water vapor from the garment microenvironment to provide cooling to the aviator, which is insufficient for current aircrew clothing systems that comprise many layers of fabrics.
In the related field of thermal conditioning of burdensome garment systems, air cooling garments have been developed such as that disclosed in U.S. Pat. No. 5,243,706 to Frim et al. The said xe2x80x9cmicro-climate conditioning systemxe2x80x9d incorporates an impermeable yet porous bladder that distributes air over regions of the wearer""s body. Although such a garment does inflate to a relatively low pressure during operation, little or no control of pressure is conceivable in the disclosed configuration and is not suitable as an anti-G protective pressure garment. In U.S. Pat. No. 6,134,714 to Uglene, a personal cooling garment is disclosed in which a liquid filled, air and water impermeable, water vapor permeable bladder is retained tightly against the wearer. As air is passed over the bladder, the internal liquid may evaporate thus drawing heat from the wearer. While it is conceivable that such a garment could be so arranged as an anti-G suit, in the disclosed form it bears no relevance to acceleration protection.
In addition to negatively enhancing thermal burden on aircrew members, the prior art related to acceleration protection, has, in many cases, increased the bladder size and shape in such pressure garments to the degree that over expansion has become a problem. In particular, some of the said pressure garments interfere with critical cockpit controls when in the full pressure mode. U.S. Pat. No. 4,674,479 to Jennings et al, teaches the use of rigid stiffeners over the entire bladder envelope to resist expansion, however, the actual shape of the inflated profile of these pressure garments has not been effectively addressed.
The present disclosure describes an improved fluid cooled pressure (anti-G) garment that can effectively reduce disadvantages inherent in currently used garments for example the thermal burden, cockpit interference, sizing adjustment, and/or maintenance and repair issues.
The main objective of the present invention is to provide an active means of cooling wearer of a pressure garment such as anti-G suits worn by aircrew members of high performance, high altitude aircraft.
A secondary objective is to further reduce the passive thermal burden due to excessive bulk in the garment system.
Broadly the present invention relates to a pressure garment particularly suited for use as an anti-G suit comprising an inner layer facing towards a wearer and an outer layer, said inner and outer layers being connected together to form an air pressure holding bladder, means providing at least one area made from air impermeable, water vapor permeable material defining a first passage means for water vapor through said inner layer and means defining at least one other area made from air and water vapor permeable material defining a second passage means for air and water vapor through said inner layer.
Preferably, said bladder is received within a pocket form between an external restraint layer and an inner lining layer positioned adjacent to said inner layer of said bladder, said external restraint layer being formed a material to limit expansion of said bladder under inflated condition.
Preferably pass throughs are provided through said inner lining through which said bladder may be inserted into said pocket.
Preferably, garment further includes releasable connector means connecting said bladder inside said pocket.
Preferably said outer layer is also provided with at least one area formed from of air and liquid impermeable, water vapor permeable material to provide some of said first passage means through said outer layer.
Preferably said inner and outer layers are made from air impermeable, water vapor permeable material that forms said first passage means.
Preferably, said garment further includes secondary restraint means composed of spaced strapping encircling said bladder and positioned between said bladder and said external restraint.
Preferably the garment further comprises limiters interconnecting said inner and outer layers at spaced locations to limit expansion of said bladder in said spaced locations.